A conventional stapler is shown in FIG. 8 and generally includes an operation arm 65 and a magazine 67, and both of which are pivotably connected to the rear end of the base 68 by a first pivot 66. A main arm 61 is pivotably connected the front end of the base 68 by a second pivot 62. The main arm 61 is mounted onto the operation arm 65, and the pin 64 is pivotably connected to the operation arm 65 and movable within the slots 63 in the main arm 61. When a force is applied at the point “P” on the main arm 61, the main arm 61 is pivoted about the second pivot 62 and the distance from the point “P” to the second pivot 62 is the first force arm “A”. The insides of the slots 63 apply a force to the pin 64 when pivoting the main arm 61, so that the operation arm 65 is pivoted toward the magazine 67. The distance from the second pivot 62 to the pin 64 is the second force arm “B”. For the operation arm 65, the pin 64 applies a force about the first pivot 66 and the distance from the pin 64 to the first pivot 66 is the third force arm “C”. Therefore, the operation arm 65 is pivoted about the first pivot 66 to allow the strike plate 651 on the operation arm 65 to eject one of the staples in the magazine 67. The distance from the strike plate 651 to the first pivot 66 is the fourth force arm “D”. When the first force arm “A” is longer than the second force arm “B”, although the third force arm “C” is shorter than the fourth force arm “D”, the ratio “A” to “B” is way larger than the ratio “C” to “D”. Therefore, the force of striking the staples can be properly increased to save the force required from the users.
Nevertheless, when the user pivots the main arm 61 downward, the force moves the pin 64 downward so that the transmission ratio A/B of the force from the main arm 61 is larger than the transmission ratio C/D of the force from the operation arm 65 to complete the stapling process. The pin 64 of the operation arm 65 is located within the slots 63 in the main arm 61, and the frequent movement of the pin 64 causes wearing between the pin 64 and the slots 63 so that when pivoting the main arm 61, a small amount of pivotal distance of the main arm 61 does not drive the operation arm 65. This affects the quality and efficiency of the stapling process.
The present invention intends to provide a stapler which improves the shortcomings of the conventional staplers.